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Leading research groups in structural power composites (SPCs) — including those from  and in the U.K., and in Sweden, in Austria, and in Singapore and in the U.S. — have published a paper that sets out the characterization and requirements and reporting protocols for this emerging class of multifunctional materials. Accessible in , researchers intend for the paper to set the groundwork for formal standard methods to be developed, which are vital for industry to assess, contrast and potentially adopt these emerging materials in future products.

SPCs could have a profound impact on the future direction of composites. By tailoring the constituents and composite architecture, researchers have developed “structural supercapacitors” and “structural batteries.” These are not only electrochemical energy storage devices but also structural materials that go beyond smart structures — rather than embedding an electrochemical cell into a composite laminate (a battery in a structure) the groups’ SPCs can intrinsically undertake two roles simultaneously (structural battery).

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It has been found that SPCs not only deliver lightweighting and efficient energy storage, but also offer a novel approach to composite design and innovation. For instance, it has been shown that SPC floor panels could power the seatback entertainment units in future electric aircraft, considerably reducing electrical wiring and providing weight and volume savings. This could also translate into more ubiquitous applications as well: phones, cars, computers, medical devices, infrastructure and so on. Moreover, the World Economic Forum has recognized SPCs are one of the .

But as with any emerging technology, particularly one which draws together very different disciplines (i.e., structural composites and electrochemistry), there are no standards for characterization and reporting. The conventions, nomenclature and standards followed by conventional electrochemical and mechanical (composite) fields are very different and combining them has proved to be challenging.

Through this paper, “,” researchers have sought to rectify this. This includes recommendations that the multifunctional performance of SPCs be reported, but that this performance should also be contrasted against monofunctional benchmarks — conventional composites and electrochemical cells that use some of the same constituents. Recommendations have also been made for reporting device performance, to ensure that the published data uses the same protocols for normalization by mass or volume, for instance. 

Perhaps one of the paper’s most important findings is the need for a universal coupon (see opening image), in which both mechanical and electrochemical characterization can be undertaken. In fact, such a coupon should permit simultaneous mechanical and electrochemical characterization, as the material would be used in practice. This would mean the “multifunctional performance” could be credibly declared and any coupling phenomena (such as mechanical strain influencing electrochemical behavior) identified. Realization of such an universal coupon, and widespread adoption of this protocol, would deliver much more reliable and convincing data for SPCs, and underpin the material development and industrialization.